1. Technical Field
The present disclosure relates to in-line sensors for flow monitoring and assuring the validity of in-line sensor response and reporting used during food handling applications.
2. Description of the Related Art
In the not too distant past much of the testing of chlorine in wash water control was done manually with simple test procedures such as test strips or drop-wise titrations. These simple test procedures were suitable for managing swimming pools and seemed to be an appropriate choice for managing the wash systems of processing lines. The test procedures were used to direct manual addition of sanitizers and wash adjuvants to such wash systems. As the desire and need for better control was recognized, however, these simple test procedures proved to be inadequate, lacking both accuracy and precision.
Thus, the food industry migrated to colorimetric procedures utilizing portable meters. This migration provided some improvement. Quantitative data was generated, and control was improved. However, with the current need for validation processes that meet the requirements of the FDA Food Safety Modernization Act (FSMA) and the need to know that a validated process was performed, these colorimetric procedures prove inadequate. They lack the necessary precision and are too slow in monitoring fluid flow path of the process stream. Without better data, it is nearly unmanageable to ensure that the validated process was performed.
There are many different approaches for calibrating in-line sensors that may provide some utility but are subject to limitations and fall short of validating in-line sensor response. For example, a first calibration approach includes assuming that a sensor is accurate by design and fabrication. However, this first calibration approach assumes there is no drift or environmental effects that will cause invalid observations, and that all sensors of a given type generate an equivalent response to the same stimuli.
A second calibration approach includes moving a sensor to an external reference fluid. However, this second calibration approach ignores the effects on the sensor of flow and local depletion of analyte. Additionally, changing the geometry and environment around a sensor can also change the sensor response.
A third calibration approach includes using a reference method to analyze a collected sample of a stream being measured, particularly, measuring a sample removed from a stream and comparing it to a reference. This approach may inappropriately assume that the sample stream is consistent enough that the determined value can be used to calibrate the sensor in spite of a time and space difference inherent in this third calibration approach.